Depends on the condition of the lawn. If it is established and in good shape, aerating will help with soil compaction, drainage (corers more so than spikers) and to some degree de-thatching. If there is excessive thatch than de-thatching with a de-thatcher might be needed. Aeration (and de-thatching) should be followed by overseeding. If the lawn is in poor shape (ie mostly crabgrass) and needs a good rejuvination, a vertical mower or slit-seeder can be used to slice into the turf, cutting slits in it. The slit-seeder takes it a step further and deposits seed in the slits. This action is potentially damaging to the root system of the existing turf, so some people say not to do it unless the lawn is in pretty bad shape to begin with. If you are clearing some ivy and brush a good tiller works best.

I would probably start with a decent push-type core aerator for yards that size and a broadcast spreader.

Don't forget to water.

I can't offer advice to pricing as I've been out of this business for 10+ years.